If I have 0$ at the moment can I make 100$ in 2 or 3 months? How?
What if I deposited 20$ .. Can I make them 100$ in less time?
It possible even you dont have money you can earn that $100 in no time if you have skills regarding developing,technical,programming,designing skills you would able to generate that money by finding jobs on this forum but if you dont have skills then it would be hard. Using $20 doesnt guarantee to make you $100,if you could able to risk that on playing gambling then its your choice.
I am able to design and have technical skills
In that case: open a thread, add your portfolio, your prices and which escrow providers you're willing to work with.
Then actively search for work, on bitcointalk and other places, refer them to your thread for pricing and/or a look at your portfolio.
If you find a couple good gigs, you can make $100 in a couple of days.
Good luck!